Merriam-Webster Collegiate Dictionary - mackenzie

 I. biographical name Alexander 1822-1892 Canadian (Scottish-born) statesman; prime minister (1873-78)  II. biographical name Sir Compton 1883-1972 English novelist  III. biographical name William Lyon 1795-1861 Canadian (Scottish-born) insurgent leader  IV. geographical name  1. river 1120 miles (1802 kilometers) NW Canada in Northwest Territories flowing from Great Slave Lake NW into Beaufort Sea — sometimes considered to include the Finlay, Peace, & Slave rivers (total length 2635 miles or 4216 kilometers)  2. former district Canada in W Northwest Territories in basin of ~ River; area now split between Northwest Territories & the W part of Nunavut